A laser device such as that described above is used as a light source in a laser system that may be, for instance, a microscope, a profile measurement device, an exposure device or an inspection device. The output wavelength of the laser device is set in correspondence to the purpose of use and functions of the system in which the laser device is installed. Laser devices in the known art include those capable of outputting deep ultraviolet light with a wavelength of 193 nm and those capable of outputting ultraviolet light with a wavelength of 355 nm. The wavelength of the laser light generated by the laser light generating unit, a specific number of rows and a specific number of stages over which amplifiers are disposed in the amplifying unit, and types of, and a specific combination of wavelength conversion optical elements included in the wavelength converting unit are all set in correspondence to the purpose of use, functions and the like (see patent literature 1).
Several methods through which light output can be turned ON/OFF at high speed in this type of laser device have been proposed. In a first art, for instance, a wavelength conversion optical system is configured with a plurality of parallel light paths (e.g., a first system and a second system) and a serial light path at which light outputs emitted from these parallel light paths enter in a superimposed state, with a light source and an amplifier disposed in correspondence to each parallel light path. Pulse light emitted from the light source and amplified by the amplifier is input to the corresponding light path, i.e., the first system and the second system, and the timing with which light is emitted at each light source is adjusted. Namely, the temporal overlap of the pulse light having passed through the first system and the pulse light having passed through the second system, which occurs at the wavelength conversion optical element disposed at the last stage in the serial path, is controlled, and through this control, ON/OFF control of the light output is achieved (see patent literature 2).
In a second art, a wavelength conversion optical system, constituted with a single serial light path configured with a plurality of wavelength conversion optical elements, includes a single set of a light source and an amplifier. Seed light emitted from the light source is switched to a high peak power state or to a low peak power state, and ON/OFF control of the light output is achieved by varying the wavelength conversion efficiency through this switchover.